A sequence of V-band light curves of the active close binary SZ Piscium
(F8 V-IV+ K1 IV),
extending from 1957 to 1998, is presented and analysed
to derive the spot distribution and evolution on the component
stars. In our modelling approach the Roche geometry and Kurucz's atmospheric
models were adopted. The resulting maps of the spot surface distribution
were regularized
by means of the Maximum Entropy and Tikhonov criteria to take full advantage of the increased geometrical resolution during eclipses. By comparing
the maps obtained with these two criteria, it was possible to
discriminate between surface features actually required by the data and
artifacts introduced by the regularization process. Satisfactory fits
were obtained assuming spots on both components and
the unspotted V-band luminosity ratio: .
The derived yearly spot distributions indicate that the spot patterns
consist of two components, one uniformly and the other non-uniformly
distributed in longitude,
the latter suggesting the presence of preferential longitudes. Starspots at latitudes higher than
~ were not required to reproduce the photometric modulation.
For the spot pattern on the less luminous F8 V primary component
there are only some hints of the possible presence of spots
around the substellar point facing the K1 IV secondary component. On the more luminous and larger secondary component there is clear evidence for the presence of three active longitudes. A stable active longitude around the substellar
point facing the primary star appears to be quite compact with an extension of ~ on several maps. The other two active
longitudes display irregular changes of the
spot area and location. The variation of the total spotted area on the secondary
component shows sizeable fluctuations and a possible short-term
cycle of about 13 yr, which is more clearly apparent in the variation of the
spotted area unevenly distributed in longitude. A longer-term cycle of about yr with a markedly non-sinusoidal variation might also be present.
The spatial association between photospheric spots and chromospheric
plages (as detected in the UV lines) appears significant for the active region
around the substellar point in the K1 IV component.
A possible connection between magnetic activity and orbital period variation is suggested by comparing the variation of the
total spotted area with the O-C diagram of the primary eclipse times.
The time span covered by the available data is, however, not long enough
for us to draw any definite conclusions.

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